Migration Velocity Profile

Husky Oil also included a geologically derived velocity model in their deliverables. The near-surface component of this model is shown in top panel of figure . The model was developed from the combination of surface geologic observations, well-ties from 8-10 nearby wells and walk-away VSPs.

 

vel_init
Figure 4 Initial velocity profile. Top: geologic velocity model; Middle: refraction tomography velocity profile; and Bottom: merged geologic and refraction velocity profiles.

Refraction tomography inversion of first-break arrival times (c.f. figure ) provided a better estimate of the near-surface velocity profile (middle panel). The top 200 m of the refraction tomography model were grafted onto the geologic model, which was subsequently smoothed to create the migration velocity profile (bottom panel). The full migration velocity profile (figure ) shows an intricate near-surface geologic environment characterized by complex faulting and folding and strong velocity contrast. Near-surface velocities are seismically fast with values ranging between 3600 m/s and 4800 m/s.

 

vel_final
Figure 5 Migration velocity profile.